The invention is based on a protective device for the laser machining of holes in at least one component by means of laser radiation, the protective device being positionable at the beam-exit-side end of a hole to be machined, in order to protect an adjoining rear space of the component from the laser radiation, of the generic type. The invention is also based on a method for producing a component such as a nozzle, in particular an injector, by using the protective device according to the invention and on a method for producing an injector by using the protective device according to the invention.
In the industrial machining of materials, in particular for the drilling of holes, such as for example through-holes or blind holes, in components or workpieces, pulsed high-power lasers are being used increasingly often, the use of which allows a higher level of precision of the machining and a shorter machining time to be achieved in comparison with conventional mechanical machining techniques. A problem with the laser drilling of holes is that the laser beam emerging from the rear side of the drilled hole upon completion of the laser drilling operation when drilling a hole has to be shielded or blocked in order to protect the component wall lying opposite the rear side of the drilled hole from undesired damage by the laser beam. This problem arises in particular whenever the components to be machined by means of laser radiation are, for example, injection nozzles or diesel nozzles or the like for use in automotive engineering. Such an injection nozzle has a substantially hollow-cylindrical nozzle body with a nozzle cap, in the cap wall of which multiple spray holes are to be provided or drilled out in order to distribute or atomize the fuel through these spray holes into the combustion chamber of the engine during the later use of the nozzle as intended. Since such injection nozzles are formed rotationally symmetrically with respect to their longitudinal axis, it is common practice in the prior art for the laser drilling of a spray hole in the nozzle cap to insert within the cavity that is formed in the nozzle cap for the machining time of the laser drilling a protective device which is formed from metallic or ceramic material, is also referred to as so-called backing material and serves the purpose of blocking or absorbing the laser beam emerging from the drilled hole that has been drilled by the laser in the wall of the nozzle cap at the rear side of the drilled hole, in order to prevent damage to the opposite wall of the nozzle cap.
A disadvantage of such protective devices according to the prior art is that the metallic or ceramic materials used for them cannot withstand the laser radiation emerging from the rear side of the drilled hole and impinging on the protective device in the case of laser machining by high-power lasers with ultrashort laser pulses, and consequently cannot perform their protective function. In this respect, FIG. 2 shows a conventional protective device 1, which when used as intended in the cavity 6 of a diesel nozzle 2 has through-holes 7 caused by a laser beam emerging from the rear side of the drilled hole, and consequently no longer has any protective function for the rear space. FIG. 3 shows by way of example a diesel nozzle 2 after failure of the conventional protective device 1, the left-hand wall of the nozzle body having a drilled spray hole 3 drilled out by means of laser radiation and the right-hand wall, which lies opposite the rear side of the drilled spray hole, displaying damage 13 in the form of a penetration by the laser beam, in spite of a protective device 1 having been inserted during the laser machining, as a result of the failure of the protective device 1 from FIG. 2.